This invention generally relates to power sources. More particularly, this invention relates to power sources employed in welding, cutting and heating applications.
Power sources typically convert a power input to a necessary or desirable power output tailored for a specific application. In welding applications, power sources typically receive a high voltage alternating current (VAC) signal and provide a high current output welding signal. Around the world, utility power supplies (sinusoidal line voltages) may be 200/208V, 230/240V, 380/415V, 460/480V, 500V and 575V. These supplies may be either single-phase or three-phase and either 50 or 60 Hz. Other power supplies, such as that available in mines or subways, may be dc. Additionally, power may be provided from generators that attempt to provide power at such voltages and frequencies, or at other voltages and frequencies, or at dc.
Welding power sources receive such inputs and produce an approximately 10-40 volt dc high current welding output. Substantial power is delivered to a welding arc which generates heat sufficient to melt metal and to create a weld. Cutting power sources receive such inputs and produce an approximately 80 volt dc high current cutting output. Induction heating power sources receive such inputs and produce an approximately 200 volt ac high current heating output. Because welding, heating and cutting require similar high power outputs, welding type power source or supply, as used herein, includes welding, plasma and induction heating power sources and supplies. Welding type power, as used herein, refers to welding, plasma or heating power.
Given the various utility and generator power inputs it is desirable for a welding/plasma/heating power supply to be able to receive any of a wide range of power inputs. Several hurdles must be overcome to allow a power supply to receive multiple input voltages. First, the power circuit must be able to receive the expected voltage magnitudes and frequencies, yet still provide the desired output voltage. Second, the desired control voltage must be provided, regardless of the input voltage. Also, when aux power (for tools etc.) is being provided, the desired output voltage and frequency (110V ac at 60 Hz, e.g.) must be provided regardless of the input voltage and frequency.
Early power supplies overcame these hurdles by having taps on transformers correspond to each expected voltage. The taps were selected by the user manually xe2x80x9crelinkingxe2x80x9d the power supply for each input voltage. This was time consuming, and required the user open the power supply. Operating an improperly linked power source could result in personal injury, power source failure or insufficient power.
A prior art welding source that improved upon manual linking provided an automatic linkage. For example, the Miller Electric AutoLink(copyright), described in U.S. Pat. No. 5,319,533, incorporated herein by reference, tested the input voltage when they are first turned on, and automatically set the proper linkage for the input voltage sensed. The power supply included two inverters connected in parallel (for 230V, for example) or in series (e.g., for 460V). Such arrangements generally allow for two voltage connection possibilities. However, the higher voltage must be twice the lower voltage. Thus, such a power source cannot be connected to supplies ranging from 230V-460V to 380V-415V or 575V.
Another prior art power supply that was a significant advance in the ability of a power source to receive a wide range of power is described in U.S. Pat. No. 5,601,741, issued Feb. 11, 1997, on application Ser. No. 08/342,378, filed Nov. 18, 1994, entitled Method And Apparatus For Receiving A Universal Input Voltage In A Welding Power Source, and is owned by the assignee of the present invention. The power supply described in U.S. Pat. No. 5,601,741 is implemented commercially in the Miller Omniline(copyright) power supply.
The welding/plasma/heating power supply of U.S. Pat. No. 5,601,741 (incorporated herein by reference), includes an input stage, a preregulator stage, and an output stage. Also, a controller (with a power source) controls the power supply to produce a desired output. The power supply for the controller is referred to as an auxiliary power supply therein. However, the present invention also includes a power output for tools etc that is often referred to as an auxiliary power output. Thus, to avoid confusion, the power output for tools will be referred to herein as aux power, and the power for the controller will be referred to herein as control power.
Generally, the Omniline(copyright) input stage receives ac utility or generator power, and rectifies that power to provide a first dc signal. The rectified dc signal is provided to the preregulator, which includes a boost converter. The boost converter boosts the rectified signal to create a dc bus. The output stage includes an inverter, transformer, and rectifier which create welding, cutting, or heating power (welding type power) from the bus.
Because a dc bus is created (by the boost converter) and then inverted to create the output power, the output power voltage and frequency is independent of the input voltage and frequency. This allows a wide range of input voltages and input frequencies to be used.
However, power for the controller is derived by transforming the input voltage. The control power circuit determines the magnitude of the incoming power, and configures taps on a transformer to obtain the desired control power. The control power transformer is relatively small since the amount of control power needed is relatively small. While a wide range of input power are thus acceptable, the input must be sufficient that, for a selected tap, the control voltage is acceptable.
Thus, the Omniline(copyright) provided the desired output voltage by inverting a dc bus having a magnitude independent of the input voltage. Also, the Omniline(copyright) created control power by selecting taps on a transformer. This allowed a wide range of input voltages to be used, but still required the input voltage to have an appropriate magnitude for being transformed into a control voltage. Additionally, this prior art did not provide an aux power (for tools), that had a voltage and frequency independent of the input voltage and frequency.
Accordingly, a welding power source that may receive any common input voltages or frequency is desirable. Preferably, this is accomplished without the need of any linkages for the welding power input and for the control power input. Additionally, it is desirable to have such a welding power source that produces aux power and weld power having a frequency and voltage independent of the input frequency and voltage.
According to a first aspect of the invention a welding type power source is capable of receiving a range of input voltages and frequencies. It includes an input circuit, a preregulator, an output circuit, a preregulator controller, and a control power circuit. The input circuit receives input power at an input frequency and an input magnitude, and provides a signal having a magnitude responsive to the input magnitude to the preregulator. The preregulator provides a dc signal having a preregulator magnitude independent of the input magnitude to the output circuit. The output circuit provides a welding type output power signal having an output frequency independent of the input frequency and having an output voltage independent of the input voltage. The preregulator controller is connected to the preregulator, and receives power from the control power circuit. The control power circuit derives power from the dc signal and provides control power to the controller that has a control power magnitude independent of the input magnitude and a control frequency independent of the input frequency.
The input circuit includes a rectifier in one embodiment.
The preregulator magnitude is greater than the first magnitude, and the preregulator includes a boost converter in various alternatives. The boost converter may include a slow voltage switched switch and a slow current switched switch.
The output circuit includes an inverter, which may include a switched snubber in other alternatives.
The preregulator magnitude is greater than the control power magnitude, and/or the control power circuit includes a buck converter in additional embodiments.
According to a second aspect of the invention a method of providing welding type power from a range of input voltages and frequencies, includes receiving an input power signal having an input frequency and an input magnitude. A first signal having a magnitude responsive to the input magnitude is provided. The first signal is converted into a dc second signal having a second magnitude independent of the input magnitude. A welding type power signal derived from the dc second signal has an output frequency independent of the input frequency and further has an output voltage independent of the input voltage. The dc second signal is converted into control power having a control power magnitude independent of the input magnitude.
The input signal is rectified in one embodiment.
The second magnitude is greater than the first magnitude, and converting the first signal into a dc second signal includes boost converting the first signal in other embodiments. Boost converting may include slow voltage switching and slow current switching a switch.
The output power signal is provided by inverting the dc second signal, and/or using a switched snubber in various alternatives.
The second magnitude is greater than the control power magnitude, and/or converting the dc second signal into control power includes buck converting the dc second signal in additional alternative.
According to a third aspect of the invention a welding type power source capable of receiving a range of input voltages and frequencies includes a dc bus. An output circuit receives the dc bus, and provides a welding type output power signal. The output power is voltage and frequency independent of the input power. A controller is connected to the output circuit. Power for the controller comes from the dc bus, through a control power circuit.
According to a fourth aspect of the invention a method of providing welding type power from a range of input voltages and frequencies includes receiving a dc bus and providing welding type power at a magnitude independent of the bus magnitude, but derived from the dc bus. The dc bus is also converted into control power whose magnitude is independent of the dc bus magnitude.
According to a fifth aspect of the invention a method of starting to provide providing welding type power from a range of input voltages and frequencies, includes receiving an input power signal and providing a first dc signal at magnitude responsive to the input""s magnitude. A second dc voltage whose magnitude is less than the first dc magnitude is derived from the first dc magnitude. A control converter is controlled with the second dc voltage such that the control converter produces a control dc voltage. An output converter is controlled with the control dc voltage to produce an output signal.